C++ String Exercises: Remove all special characters from a given string

Last update on April 11 2025 12:48:22 (UTC/GMT +8 hours)

22. Remove All Special Characters from a String

Write a C++ program to remove all special characters from a given string.

List of special characters: ., !, @, #, $, %, ^, &, \, *, (, )

Sample Data:
("abcd $ js# @acde$") -> “abcd js acde”

Sample Solution-1:

C++ Code:

#include<algorithm> // Standard library that includes various algorithms
#include <iostream> // Input/output stream library
#include <vector> // Standard vector library for dynamic arrays

using namespace std; // Using the standard namespace

// Function to filter special characters from the input text
std::string test(std::string text) 
{
	std::string result_text; // Declare an empty string to store the filtered characters
	
	// Loop through each character in the input text
	for(int i = 0; i < text.length(); ++i)
	{
		// Check if the character is a letter (uppercase or lowercase), space, hyphen, underscore, or digit
		if((text[i] >= 'a' && text[i] <= 'z') ||
			 (text[i] >= 'A' && text[i] <= 'Z') ||
			 (text[i] == ' ') || (text[i] == '-') ||
			 (text[i] == '_') ||
			 (text[i] >= '0' && text[i] <= '9'))
		{
			 result_text.push_back(text[i]); // If it matches the allowed characters, add it to the result string
		}
	}
	
	return result_text; // Return the string containing filtered characters
}

int main() {
  string str1 ="abcd $ js# @acde$";
  cout << "Original string: " << str1; // Output the original string

  string result = test(str1); // Call the function to filter special characters
  cout << "\nNew string after removing the special characters from the said string:\n" << result; // Output the resulting string after filtering
}

Sample Output:

Original string: abcd $ js# @acde$
New string after removing the special characters from the said string:
abcd  js acde

Flowchart:

Sample Solution-2:

C++ Code:

#include<algorithm> // Standard library that includes various algorithms
#include <iostream> // Input/output stream library
#include <vector> // Standard vector library for dynamic arrays

using namespace std; // Using the standard namespace

// Function to filter special characters from the input text
std::string test(std::string text) {
    std::string result_str; // Declare an empty string to store the filtered characters

    // Loop through each character in the input text
    for(int i = 0; i < text.size(); i++) {
        // Check if the character is a digit ('0' to '9'), uppercase letter, lowercase letter, hyphen, underscore, or space
        if ((text[i] >= 48 && text[i] < 59) || (std::toupper(text[i]) >= 65 && std::toupper(text[i]) < 91) || text[i] == '-' || text[i] == ' ' || text[i] == '_') {
            result_str.push_back(text[i]); // If it matches the allowed characters, add it to the result string
        }
    }
    return result_str; // Return the string containing filtered characters
}

int main() {
    string str1 = "abcd $ js# @acde$";
    cout << "Original string: " << str1; // Output the original string

    string result = test(str1); // Call the function to filter special characters
    cout << "\nNew string after removing the special characters from the said string:\n" << result; // Output the resulting string after filtering
}

Sample Output:

Original string: abcd $ js# @acde$
New string after removing the special characters from the said string:
abcd  js acde

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C++ program to filter out non-alphanumeric characters from a string and print the cleaned result.
• Write a C++ program that reads a string and removes all punctuation and symbols, leaving only letters and spaces.
• Write a C++ program to iterate over a string and build a new string that excludes all special characters.
• Write a C++ program to process a string and output it with special characters stripped out using ASCII checks.

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Previous C++ Exercise: Check if a string is a subsequence of another string.